fc1jz

Ok here is the background. I have a 93 5spd. I recently installed a t70 turbocharger kit I pieced together. At the same time I upgraded my ecu to PFC with commander, installed 1600cc secondary injectors, FPR and braided fuel lines. I also removed everything from the UIM besides the air temp sensor. I also installed a wideband o2.
I put a map in the PFC I found for a t66 as a baseline to tune from.
I can drive the car easy to redline with no problems, I can even get partially on the throttle and boost 1bar to redline as long as I feather the throttle. The problem is when I floor it, Everything seems fine, huge power, quick spool, everything you want from an rx. Then at about 5k if boost is over 1.1bar, it feels like I get ignition cut. The car basically stutters really hard and then revs a little more (albeit roughly) and then stutters again, revs, stutters, does this all the way to redline.
One thing I noticed is that the wideband is reading an afr between 9:1 and 10:1 near the stutter. So I definitely know it is not any lack of fuel causing the problem. Could running rich be causing the stutter? Like maybe its so rich it is putting out the spark from my iridium plugs?? I know most people tune for 10.8-12:1 depending on boost level. And I am in the low 10s to mid 9s in boost.
During the stutter it almost sounds like a Pop, because it happens so fast. I am assuming from the excess fuel igniting in the hot manifold.
Oh, also during the "conversion" I relocated the battery behind the passengers seat. Could bad grounding to the battery be causing this??
I am posting this in the single turbo section and the PFC section since these problems could stem from either of these mods.

racerxrx7

I'm actually in the same boat. I have a GT35/40 and it's doing the same hesitation when I stomp on it. I still haven't tuned mine, so I'm thinking it's leaning out between 4 and 5.5k. I've enriched those cells a little and it seems to help. Once I get it tuned, I'll be able to diagnose a little better. You really need to get it tuned correctly with the right maps. I know it's not much to go on but you are not alone. Try enriching those cells around 4 to 5.5k rpm to see if it helps or lean it out. That might work.

$150FC

what do you guys have for ignition mods?

RxDriver

I don't have any ignition mods. Just Denso iridium plugs.
But I think I fixed the stutter. It was getting into 9:1 zone on afr, so I reduced lag correction to -.10 for the secondaries to reduce fuel (the map I had was for 1300cc secondaries and I am running 1600ccs), and now the hesitation is gone, but after I drive it hard, the damn car doesn't want to idle. It idles low at 4-500rpms and bucks until about 1500 when I get on the throttle. I think it may be the grounds in my car, so I will check those and make them better. I am now idling around a 13:1 afr.

Also, since I reduced lag on the secondaries the car has a more noticeable injector transition at around 4500 making afr's nearly 15:1 in that area. Then afrs settle to 10.5:1 all the way to redline.

Does anyone think the rough idle could be because I fouled a plug from running to rich?? Or bad grounds???

suganuma

what heat plugs are you running? That may be your problem.

Ported motor?

Right now, I'm running very rich as well. I can run WOT through all RPMs without hesitation on 10.5 plugs in the leading. I fouled one of them out putting around town and changed them out with 9s. It stutters like you are describing at higher rpm under boost with the 9s. I am also running an MSD 6A amp on leading.

suganuma

Most rotaries like a richer idle from what I've seen. 12.5-13:1 seems to be pretty typical.

Yes, a rough idle and poor high end could be caused from fouled plugs. Be aware that fresh plugs will also combust the mixture better over the complete RPM range and this will affect any tuning you did on the fouled plugs. i.e. you might want to add a little extra fuel back in if you took any out.

CCarlisi

It sounds like you're flooding it with fuel. When Steve Kan tuned my friend's car it did the same thing when the afrs fell below 10, and he has an upgraded ignition.

suganuma

Exactly. I guess I wasn't very direct in my replies. My mixture is currently so pig rich that I HAVE to run very cold plugs to get it to even ignite the mixture.

You should be able to find a decent base map to tune from that uses 550/1600 injectors on a T66/T70 turbo. You stated that the map you are using was made for 1300cc injectors. The 1600s will outflow them by quite a bit. I didn't hear you say that you have the datalogit, but from what I understand that will be necessary for you to do any real tuning with the PFC.

3200-2600=600cc more fuel...

fc1jz

Yeah, I set the secondary injector lag to -.06 to compensate some. Seems to have cured the stutter, but now the injector change is much more noticeable and lean. I don't want to drive hard until I tune each cell properly with my wideband. I also found out my wastegate is sticking open, I think that has alot to do with my bad idle. And it explains the sudden loudness of my car. So I still have a few things to fix also. Funny thing is the turbo still builds boost from 2k and is fully boosted by 4k
The plugs I run are denso iridium IRE01-27#4. The heat range is 27, the coldest denso offers in this iridium. I have another set, but I don't want to keep fouling them, they are like $25 a piece. What type of plugs are you guys running? Should I go with a more inexpensive plug in a colder range? I am tuning afrs for 11:1 pretty much from 0-20psi. And anything below that I am tuning for 13:1.
Also as far as my plugs go, could it be that they have too much buildup from running so rich? Maybe just need to clean them?